Double-range voltmeter



Aug; 24 1926.

E. F. WESTON DOUBLE RANGE VOLTMETER Filed August 26, 1925 2 Sheets-Sheet 1 Aug. 24 1926. I 1,597,256

E. F. WESTON DOUBLE RANGE VOLTMETER Filed August 26 1925 2 Sheets-Sheet 2 4 ed to the low range bindin post 3 or the Patented Aug. 24,1926.

UNITED STATES PATENT OFFICE.

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JERSEY.

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7 Application and August as, 1925. Serial 1'. saesa.

, This invention relates to a double range voltmeter for indicating voltages of either a higheror a lower range of Values. The invention resides in an attachment adapted to 6 be connected to the back of voltmeters of (known type, such attachment containing a. high range resistpr and switching means for making the necessary connections to enable the voltmeter to indicate higheror lower ranges of voltages. I

In the drawings:. Fig. 1 is a side elevation with parts shown in vertical section on a diametrical plane; Fi 2 is a bottom view partly in section on t e horizontal plane indicated by line 2-2 of Fig. 4.

Fig. 3 is a front elevation of the attachment to the right of plane 33 of Fig. 1; Fig. 4 is a rear view; Fig. 5 is a diagram of the circuit connections. g I v 1 Referring to-Figs. 1 and 2, G represents a voltmeter of the known movable coil type,

the coil K (see Fig. 5) being in circuit with a lowsrange resistor O mounted inside the case. 1 and 2 are the main negative and positive terminals, in this instance servin also as a means for securing the attachment to the base of the voltmeter. 7

The attachment comprises a disk-shaped memberL, preferably of the same diameter as the base of the voltmeter, having secured within it a *high range resistor coil M.

The negative terminal 1 of the instrument projects through the member L and serves as one terminal of thecomplete assembly, while the positive terminal 2 of the voltmeter does not extend beyond the member 7 L but is adapted to be electrically connecthigh range binding post 4 w ich are carried by the member L. A conductor 5 connects the binding st 3 witha switch contact A which 'exten s through the back of the attachment and which is normally engaged by r the free end of a sprin contact arm 6, the

other end of the arm '6 ing attached to the positive terminal 2 of the voltmeter. The

.binding post 4 is connected through the high range resistor coil M to a post 20' carrying a spring arm 7 having acontact B thereon. The outer face of the member L is recessed as at 21. to receive the fixed end of the v contact. arm -7,'-the end of the arm engaging the sides of the recess 21 with a comparathrough an aperture in the flange tively close fit, whereby the arm 7 is held in positionto place the contact B in horizontal alignment wit-h the low ran e contact A. The switch arm '6 -is simi arly confined against relative rotary motion by the walls ofthe -recess 22 in which the fixed end of the arm is held by .the terminal post 2.

The switch arm 6 may be moved from its normal position in engagefnent with the contact A and into engagement with the contact B by means of an operating rod 8 which has a reduced end 8 extending of the instrument housing and which at its opposite end carries a shouldered insulating bushing 9, the reduced outer end of which extends through an aperture in the free end of the switch arm 6. 1 Y While not limited in its application thereto, an instrument of'this type is particularly useful in connection with radio recei vers and a typical diagram of 'circuit connections is illustrated in Figure 5. As

illustrated the switch arm 6 which is arranged to lie normally in contact with A serves to connect the movable coil "K and the A-battery.

If a higher range voltage, such as that 4 through the movable coil'and both high and resistor coils, thus enabling the higher low range voltage to be indicated by the voltmeter.- V

I It will be noted that the switch operating rod 8 is not positively connected to the instrument housingor to they switch arm, but

is held imposition between the instrument flange and the switch arm 6 when the at tachment base L is connected to the instru ment housing by the instrument terminals 1 and 2. Thepositioning of the spring arms 6 and 7 by locating the ends thereof in recesses formed in the member L simplifies the construction since but one post or attaching member is employed for each spring arm. The construction is also simplified and the "danger of an accidental short-circuiting of parts of the switch mechanism is reduced by the location of the lead 5 at the innerside of the disk memb er L.

It will be understood that the invention is not limited to the exact details of cong the low range resistonC in circuit across st ruction herein shown and described since various changes in the parts, thelr relatlve size, shape and location may be made without departing from the spirit of my invention as stated in the following claims. .a

I claim: i

1. An attachment to be connected to the base of a voltmeter for permitting the indication of voltages of different orders of connected to said low range binding post, a high range resistor 0011 earned by said member and having one end thereof connected to said high range binding post, a second contact having one end thereof connected to said high range coil and having its outer endin alignment Withsaid first contact, a spring switch arm having one end fixed to said member and having the free end thereof positioned between said contacts, and an operating rod'having reduced portions at each end thereof, said reduced portions adapted to be positioned within apertures in the voltmeter flange and in the end of said switch arm, respectively.

' 2. The combination with a single range voltmeter, of an attachment mounted at the rear thereof and carrying a high range resistor coil, switch mechanism for alternatively placingsaid coil in or out of circuit with said' instrument, and- .a longitudinally movable rod for operating said switch mechanism, said rod extending through the instrument flange and the switch arm, and having shoulders for confining said. rod between said flange and said switch arm.

3. An attachment for converting a single range voltmeter into a-double range instrument, said attachment comprising a member of insulating material having'apertures therethrough for receiving the voltmeter terminals, a high and a low range binding post carried 'by said member, a multiplier coil on said member, a pair of switch contacts 1n longltudinal alignment, one of said contacts being connected to'said low range binding post and the other contact being connected to said high range binding post through said multiplier coil, a'sprlng switch arm having an end adapted to contact with a terminal of the voltmeter when the atta'chment is secured thereon'and having a free end lying between said contacts, anda longitudinally movable operating rod for said switch arm, said rod having a reduced end portion adapted to be supported by the casing of the voltmeter to which the -attachmerit is fixed. 4. An attachment for converting a single range voltmeter to a double range instrument', said attachment comprising a disk member having apertures therethrough for receiving the voltmeter terminals, a multiplier coil, a pair of binding posts and switch mechanism for alternatively establishing the indicating circuit through one or the other of said binding posts, said switch mechanism including a spring switch arm and a spring contact arm having the free ends thereof in'longitudinal alignment and having the fixed ends thereof positioned in and snugly engaging the sides of recesses found in the member.

5. An attachment for use with a single range voltmeter, comprising a disk member, a multiplier coil thereon, a pair of binding posts and'switch mechanism for establishing the indicating circuit through either of said binding posts, said switch mechanismincluding a contact extending through said member, a connection .at theinner face of said member and connecting said contact to one of said binding posts, a spring switch arm and a spring contact arm at the outer face of said member and having portions.

thereof in longitudinal alignment with said first contact. 1

6. An attachment for connection to the base of ;a voltmeter having a housin vided with a flange at the forwar face thereof, said attachment comprisin a disk the body exten ing beyond said member and in' on-.-

gitudinal alignment with the flange of an instrument to which said attachment is fixed,

and a switch operating rod having a reduced portion positioned in the aperture of said switch arm andhaving a reduced portion at the opposite end thereof adapted. to pass through an aperture in the instrument flange.

ture.

EDWARD 1 WESTON.-

In testimony whereof I affix my signae 1-10- 

